Direct-current gyrocompass



SPt 17 1.929" c. B. MlLLs i 1,728,185

DIRECT cuRmgn Gmocogqns;

Original Filed March 15. 1921 2 Sheets-Sheet 1 Spt. 17, 1929. v B. MILLS1,723,185

' DIRECT CURRENT GYRocourAss y Original Filed March 15. 192-1 2Sheets-Sheet 2 lllllm. E

Patented Sept. 17, 1929 1 UNITED STATES. PATENT OFFICE CHESTER B. MILLS,OF BROOKLYN, NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, '.l() SPERRYGYROSCOPE COMPANY, INC., A CORPORATION 0F NEW YORK DIRECTvCURRENTGYROCOMPASS l Application led March 15, 1921, Serial No. 452,505.Renewed February 6, 1923.l

This invention relates to gyroscopic compasses, one of the principalobjects being to reduce the present high cost of these instruments. Afurther object ofthe invention is to improve the details ofconstruction-whereby compasses are rendered less sensitive to disturbingforces and more rugged in construction. AA further object of theinvention is to render possible the utilization ofdirect current for thedriving of the ,gyro rotor instead of alternating current as hasheretofore been universally employed, and the employmentof a single linevoltage for all the electrically driven parts.

now consider the preferred form of my invention, is shown:

Fig. l is a side elevation partly in section of a compass and itsmounting constructed according to my invention.

' Fig. 2 is a detailed top View ofthe trolley or contact wheel mountedon a follow-up member.

Fig. 3 is wheel.

Fig. 4 is a side elevation of the trolley and ,co-operating contactblock.

Fig. 5 is a front elevation partly in section of the gyro compass, therear half of the rotor casing being removed to show the motor.

Fig. 6 isa diagrammatic view the effect ofthe earths magnetic field on adirect-current motor.

The compass is shown as mounted Within a cylindrical housing which ispreferably formed entirely of magnetic material such as sheet iron so asto shield the compass from the influence of the earthsmagnetic field ashereinafter explained in detail. For this purpose the compass is closedat the bottom by an iron plate 2 as Well as at the sides, although ifthe compass is secured to an iron deck the a sectional view of thetrolley latter plate may be dispensed with. At the top a heavy iron ring3 is provided for the same purpose as Well as the sheet metal hinged top4 so that even though the top 5 is of glass in order that the card 6 maybe seen, the earths field will' be substantially eliminated by the massof iron near the top.: Card-6 is preferably made of solid opaquematerial,

-vvith a pair of arms Referring to the drawings in Which what 1 such assheet metal, so that when the compass is viewed through the cover 5 themechanism thereof is concealed by a card so that in appearance thecompass is not dissimilar to a large magnetic compa'ss1 The gimbal ring755 supporting the compass proper is shown as suspended by springs 8 froml'said heavy ring 3. The second ring 9 is supported on horizontal pivots10 and 11 within ring 7, said second ring supporting, in turn, thespider 12 on 6o horizontal pivots 13, and 14 at .right angles to pivots10 and 11. Said spider is provided 15 which support the main frame Work16 ofthe compass.

Heretofore it has been the practice to suspen'd the follow-up systemfrom said frame Work` and to mount the card underneath the same. Iprefer, however, to mount the com pass card 6 entirely above the spiderso as to cover all parts of the compass beneath. For 7o this purpose theouter follow-up frame 17 is provided with a central hollow stem 18extending above the support 16 and to which the card is secured. Said'stem is journalled for rotation in the enlarged central portion 19 ofsupport 16 by a plurality of anti-fric'` tion bearings 20, 21 and 22, atleast one of which, 21, acts as a thrust bearing to support the Weightof the compass. From the top of said hollow stem 18 is suspended abundle of 80 illustratingfine wlres 21', said wires being secured at thetop Within adjustable member 23 and supporting at the bottom thevertical ring 24 of 'the compass. Within/"said ring is supported in theusual manner` the rotor casing 25 on 85 horizontal pivots-26.

The' follow-upframe 17 has secured thereto the usual large gear 27 whichis driven by reversible motor 28 operating through reduction gears 29,said gears also being provided with an eccentric groove 30 for thepurpose of applying corrections to the compass reading. For thispurpose, a correction mechanism 31 ofany desired form is shown assecured to the exterior support 16, said mechac5 nism having an arm 32pivoted at its lower end having a roller 33`engaging said eccentricgroove. It would be evident th'at as the ship turns, the eccentricgroove will rotate leverA 32 and thereby eiect the movement of the 100may be covered by screen 'reference or lubber ring 34 after thecorrecslightly to one side of the center of the shaft to make room forthe motor armature 38 and commutator 39 placed directly on the shaft.The rim of the rotor, however, extends laterally toward and beyond thecenter of the shaft. The field poles 4() and 41 project from the side ofthe casing Within the overhang of the rotor rim so that the rotorsubstantially encloses the armature and poles. Preferably, the motor isof ythe bi-polar type. Ventilating apertures 42 and 43, the upper one ofwhich 44 provide free circulation of air within the casing so that themotor` maybe properly cooled.- No provision is made, therefore, forexhausting the casing of air, the motor being made of suiiicient powerand of sufficient cooling characteristics to drive the heavy rotor atsufficient speed against air friction.

I have found by many experiments that 1n all direct current motors thereis a leakage of flux 49, 49" from the outside of each of the poles N, Sas indicated in Fig. 6 although, of

` course, the larger portion of the flux Hows between the poles as shownat 50. While such leakage causes little or no trouble in the averagemotor; in a gyro com ass it may cause serious diiiiculty since t emagnetic iield set up thereby would be influenced by the magnetic iieldof the earth unless precautions were taken to prevent the same. Thus, ina bi-polar type motor with the poles arranged horizontally and the motorplaced w'ith the armature shaft extendingnorth south, the magnetic fieldbetween the poles would be disturbed by the earths ield so that a torquewould be exerted on the motor when the compass is `really pointingnorth, thus causing a deflection of the gyro compass if said motor weredriving the same. This condition is represented Fig. 6 wherein a torquewould be exerted in the direction of the arrow. By arranging the polessubstantially vert-ical, however, I find that the effect of the earthsfield is reduced to a minimum, since the lines of force then cross eachother substantially at right angles so that there is no deflectionexcept that due to the inclination of the earths fieldl or the magneticdip. This last force being about the horizontal axis and slight does not[affect a gyro compass to nearly as great an extent as a torque aboutthe vertical axis. However', in order to further reduce the effect ofthe earths field', including both horizontal and vertical components,Iprefer to encase the rotor 35 is supported on a cendiagrammatically inthe entire gyroscopic compass inmagnetic material, as above described.By such or similar means, not only is the influence of the earthsmagnetic field reduced to a minimum but also the influence of any othermagnetic field in the vicinity of the compass,'such as that due to heavycurrents passing through bus bars near the compass etc. Also it will beunderstood that the magnetic shield employed may be the ships hullitself, Where it is possible to arrange the compass so as to besubstantially surrounded by iron, as on a submarine. A I y For impartingmeridian seeking properties to the compass, I prefer to substantially.bal-i ance the casing 25 about pivots 26 and to pivot on the follow-upframe 17 by means of pivots 63, `a support or ring 64carrying a pair ofcontainers 65, 66 adapted to contain a heavy liquid, such as mercury.Said containers are connected by a tube 67 of small bore,'the theory ofoperation being fully setA forth in the U. S. patent to Harrison et al.No. 1,362,- 940-gyroscopic compass, filed December 21, 1920. Said ring64 is connected to the gyro-casing 25 eccentrically by means of pin 68on arm 69 so that no separate damping means is necessary. The employmentof the -f mercury ballistic in connection with a direct currentgyro-compass has especial advantages since a slight wear in thecommutator or brushes ofthe driving motor resulting in lessening theweight on one side of axis 26-26 will not result in a material out ofcillations ofs'mall amplitude to the follow-up element 17 as hereinafterdescribed. Said element as above stated, supports the mercury containerson pivots 68. The continuous oscillation of the follow-up elementconsequently maintains the mercury containers in a state of oscillationand thereby prevents surface tension or any tendency of the mercury toadhere tothe walls of the containers or connecting tube 67, fromaffecting the sensitiveness of the apparatus, since the continuousoscillations break down any temporary condition of this nature andassure the fact' that at all times the surface of the mercury in vthetwo containers lies in the same' horizontal plane.

vIn my design of gyro-rotor and casing, I have succeeded in producing amore symmetrical casing than heretofore by reducing the diameter of therotor, and increasing the length of the rotor shaft to make room for thecommutator,etc. -In addition, the rotor end 121 of the casing is made toconform substantially ,to the commutator ed 122, the object being tosecure as equal moments about all axes as is mechanically possible. Inaddition to making the rotor casing symmetrical, I prefer to securecompensating Weight 62 and 62 to the vertical ring 24 for the purpose ofequalizing the moments of inertia. about all axes due to thestabilization of the rotor casing, as explained in Patent 1,499,322issued June 24, 1924, to Harry L. Tanner.

For driving the rotor, the repeater system and the follow-up system, Iprefer to employ the same line voltage (65-70 volts) so that no`auxiliary machinery need be employed and the numberof wires enteringthe compass reduced to aminimum, thereby reducing the number of. sliprings 4120 on the compass to four.v Hereto'fore, it has been thepractice to employ 90 volts A. C. for therotor and 20 volts D. C. forthe follow-up and repeater systems. To handle the higher voltage employed in my -follow-'up system, I have de'- Vised improved reversingcontacts forV the follow-up frame. As shown, a pair'of `reversingcontacts is secured to each side of the frame 17 While cooperatingtrolleys 70 are secured to oppositely extending arms 71, 72 of verticalring 24. Such parts are shown in detail in Figs. 2 to 4. 'e The trolleywheel is composed of a small wheel 75, preferably of alution with Monelmet-al -pins 80, 81. Bracket screw 104 may also be l minum to reduceweight, and a rim 7 6 of gold,

or similar metal. The hub thereof is provided-with' an inserted. metalbearing block 77 of special characteristics,` each end of theybearingvpin being provided with a counter bore 79. Taking in said boresare a pair of small pins 80, 8,1 extending oppositely from spring-forkpivoted at 91, 92 tovblock 93. Pressure of the trolley is supplied by aspring extending between arm 96 of the spring fork 90 and pin 97 onbracket 93. Since the bearingsrof the trolley cannot be lubricatedWithout interposing resistance in the circuit,

I prefer to employ two metals for the pins and bearing points having lowcoeicients of friction without sacrificing wearing qualities; I havefound German silver an excellent metal for the block 7 7, when used inconnec- 93 is detachably .clamped to'arm 71 or 72 as by means of boltand nut 101, a tongue and groove connection 103 being provided betweensaid bracket and base-102 so that the trolley will also be properlyaligned. A set' ing the'trolley in a vertical plane.

The contact blocks proper, which cooperate with' each trolley comprise apair of spaced blocks of metal (not shown) .and mounted in a block ofinsulation 84 detachably and adjustably clamped to the bracket 85. Theblocks preferably havea 'base of a baser metal, but adjacent theinsulating space, I preferito insert'strips of pure ttungsten or' likemetal such as molybdenum, so that the break occurs on tungsten to gold.Remarkable results have been obtained with provided for adj ustthisCombination, the remarkable conductivity, comparative softness,smoothness and ductility of the vgold complementing and cooperatingwiththe harder, tougher and high resistance tungsten to produce -a makeand break contact of exceptional wearingqualities. Such a contacthas.especial adaptation to compass work since in this type of compasswherein a continuous hunting of the fr ame takes place, contact is madeand broken at least three times a second, which in one monthofcontinuous operation amounts to about 7,800,000 contacts. The adjacentedges of the tungsten blocks are sharpened to form knife edges, theedgebeing substantially unaffected by the constant rolling back,v andforth ofy the softer' gold trolley and the constant making and breakingof'electric contact.- Obviously, any metal of like pro erties to goldmay be used for the trolley is esired,.such as silver or copper; both ofwhich are good conductors andl comparatively soft, but gold possessesthe superiority of not tarnishing and keeping its surface smoothand'b'right .even though sparking` occurs at the surface thereof. Afurther aid to the Wearing quality'of these contacts isv the fact thatduring the continuous oscillations of the follow up support carrying thecontact blocks, the trolley slowly revolves on pivot pins 8,0, 81, thuspresenting continually anew Wearing face. The cause of this rotation orcreeping has been found to 4be d ue to the Vfact that more pressure isexerted on the trolley wheel in one direction than the other due to thefact that pivots 91, 92 are to one side of pins 80,

81 and to the action of spring 95. As shown in Fig. 2, in one directionthe trolley is sub-v ]ected ta wedging action because when theU.contact-blocks are being pushed'downward- 110." thus lessening thepressure ex- 1 erted by spring 24. The result is that there' is moretendency toslip inone direction than in the other, resulting in thecreeping effect above described. This feature and the con-v struction ofthe trolleys and contacts arel not claimed herein but are reserved formy divisional application No. 609,329, led'December 27, 1922.

j In accordance with the provisions of the patent statutes, I haveherein described the principle of operation of my invention, togetherwith the apparatus, which I now consider to represent the bestembodiment'thereof, but I desire to have it understood that Itheapparatus shown is only illustrative and that the 'invention can becarried-out by other means. .I Also, while it is designed to use thelvarious features and elements in the combination and relationsdescribed` some of these may be altered and others omitted withoutvinterfering with the more general results outlined, and the inventionextends to such use. Having described my invention, what I claim anddesire to secure by Letters Patent 1s l. In a gyro compass, thecombination with a gym-rotor, of a direct current motor for driving thesame having a single pair of poles arranged substantially vertically forthe purpose specified.

2. In a gym-compass, the combination with a gym-rotor, of. a directcurrent motor for driving the same having a single pair of polesarranged substantially vertically and a shield of magnetic materialaround said compass for the purpose specified.

In a gym-compass, the combination of a supporting means rotatable abouta vertical go axis, of a unitary rotor and driving motor,

a casing therefor in which the rotor is journalled, said casing and itssupported parts being substantially symmetrical about all axes, andmasses supported by said means to compensate for the stabilizing actionof the rotor on the casing.

4. In a direct current gym-compass, a sensitive element mounted forturning about a vertical axis and oscillation about a hori- .o zontalaxis, including a direct current motor having a commutator for drivingthe rotor. and liquid containers connected with said element to impartmeridian seeking proporties to the compass and to automatically restoreequilibrium to the compass, if it is disturbed by commutator wear.

In testimony whereof I have aiiixed my signature.

CHESTER B. MILLS.

